[SofaGeneralAnimationLoop] MechanicalMatrixMapper: adds template

[EulalieCoevoet]

The PR just adds the template "Vec1,Vec3" to the component MechanicalMatrixMapper.

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[damienmarchal]

Hi Eulalie,

The template instantiation part (in the .cpp) is not synchronized with the extern template part (in MechanicalMatrixMapper.h).
But we can update that in a separate PR

[epernod]

I would add the extern template in the header in this PR. Otherwise we will forgot to add it ;)

[damienmarchal]

Actually we already forgot others :)

[EulalieCoevoet]

No problem :)